Steel cold (rolling) work rolls have conventionally employed forged steel containing 5-7 wt % Cr. Recent years have seen greater application of so-called semi high-speed steel work rolls containing small amounts of Mo, V, W, etc., such as the work rolls disclosed in Japanese Examined Patent Publication No. 61-11310 and Japanese Examined Patent Publication No. 7-68588.
Such conventional cold (rolling) work rolls are subjected to complex processes involving formation of a steel ingot by electro-slag remelting, followed by quenching and tempering through a forging step. During heat treatment, severe quenching by rapid cooling from high temperature is effected using techniques such as progressive induction heating and water quenching, in order to ensure a high hardness of HS 90 or greater. Electro-slag remelting which has conventionally been applied as a method of forged cold (rolling) work rolls gives a slow solidifying rate, so that the crystal grains or carbides tend to be coarse. Because of quenching cracks which occur during quenching when the crystal grains or carbides are coarse, a prior forging step has been essential to ensure sufficient material strength and ductility. From the standpoint of component design, it has been necessary for the C content to be kept to about 0.9 wt %, and all alloys such as Mo, V and W to be restricted. For these reasons, there has been a limit to the improvement in abrasion resistance of such work rolls.
It is known that roll surface hardness is greatly affected by the compression residual stress of the roll surface. For example, in order to ensure a high hardness it has been proposed to purposely provide a high residual stress, such as indicated in Japanese Unexamined Patent Publication No. 5-169112. Also, since the structure of conventional work rolls is an integral one wherein the roll and axis portions consist of the same component system, the internal material strength of the roll body is very high. As a result, the compression residual stress of roll body portions has been at a very high level of 70 kgf/mm.sup.2 or greater. It is therefore common for severe spalling to occur from defects in the roll interior or cracks produced on the roll surface during rolling, so that improvements in breakage resistance, or spalling resistance, have been desired.